Will We Ever Make It to Stars Outside Our Solar System?

May 10, 20186 min read

Since the beginning of the space exploration, we have achieved a great many things. We have successfully launched people on the moon, landed rovers on Mars and even on Titan, one of the natural satellites of Saturn. Today, we have man-made satellites all over the solar system, but have you ever wondered when will be able to reach another star?

I mean is it even possible? Voyager 1, the farthest man-made probe left the solar system four years ago or so and was launched way back in 1977. After more than 40 years of travelling, the unmanned probe is now at the distance of 21 billion kilometers from the Sun with a steady velocity of 16.99 kps. It is also the fastest spacecraft to leave the solar system.

Some would say, if we can do that, reach the outskirts of our solar system, then we can definitely reach other stars. Well, let’s not jump into any conclusion right away.

Reaching Proxima Centauri, The nearest star to Earth

According to Einstein’s special relativity, the speed of light is the highest limit at which any matter or information can travel in the universe. Although, it’s generally associated with light, in reality it is the speed at which all massless particles travel in a vacuum. The exact value of the speed of light is 299,792,458 m/s.

Four closest star system to the Sun Image Courtesy: NASA

The nearest star to our planet, Proxima Centauri is more than 4 light years away. That means, even the light from the star travelling at the speed of 299,792,458 m/s would take four years to reach the earth and vice versa.

Due to its relative proximity, the star system has been one of the possible flyby destinations for the first interstellar space travel. Researches have found out that the star is currently moving towards us at an estimated rate of 22.2 km/s. With that speed, the star system will come within 3.11 light years from the earth after 26,700 years.

The Voyager 1 is travelling at a speed of 17,000 m/s relative to the Sun. But the fastest man-made is the Helios B probe launched to study Sun’s process, which recorded a maximum speed of 70,220 m/s or 252,792 km/h. So, if by any chance the Voyager probe was heading towards the Proxima Centauri at a steady speed of 17,000 m/s, it would take over 76,000 years to cover the distance.

On the other hand, if a probe is able to attain the ground breaking speed of Helios B, then it would take no less than 19,000 years to reach the red dwarf. The latter sounds better, but it is still not viable.

The current state of space travel technology

The technology we use today is bound to be improved and that includes the technology we use in space travel. Currently, one of the most advanced form of propulsion used in spacecrafts is the ion drive engine. There was a time when ionic propulsion was considered a science fiction but today it is completely different.

In recent years, the ion thrust technology is used in various ongoing interplanetary missions, including Deep Space 1 and Dawn. It was also used on ESA’s SMART-1 lunar orbiter, which successfully completed its mission in 2006. Now, if we use ionic propulsion in our quest to reach Proxima Centauri, the thrusters would require a huge quantity of propellant (xenon).

If we assume that 82 kilos of xenon (maximum capacity of Deep Space 1) drives the prove at a maximum velocity of 56,000 km/hr, then it would take the probe more than 81,000 years to reach Proxima Centauri.

Gravity Assist Method

Apart from advanced thrusters, space travel can also be made faster with the successful implementation of Gravity Assist method. It involves a spacecraft using the gravitational force of a planetary body to alter its speed and trajectory or path. Gravitational assists are a very useful technique to conduct space missions.

In 1974, NASA’s Mariner 10 became the first space mission to use Venus’ gravitational pull to slingshot it towards Mercury. Then in the 1980s, the Voyager 1 probe used Jupiter’s and Saturn’s gravitational field to attain its current velocity, which drives it into interstellar space.

Here is what Future Looks Like

EM Drive Prototype

Electromagnetic (EM) Drive

One popular futuristic concept is the Radio Frequency Resonant Cavity Thruster or simply EM Drive. The main idea behind this technology is to produce thrust from electromagnetic field inside a cavity. It was initially proposed by British scientist Roger K. Shawyer back in 2001.

In 2015, scientists confirmed that EM Drive enabled spacecraft could make a trip to Pluto in just 18 months (New Horizons achieved that feat in 9 years). However, researchers don’t have a clear idea on how it would work. Based on that calculation, an EM Drive spacecraft bound to Proxima would take more than 13,000 years to reach their. I think we are getting closer, but not quite there yet.

Then there is a concept of spacecrafts using nuclear engines. An idea that NASA has been pondering for decades. In a Nuclear Thermal Propulsion (NTP) rocket, deuterium or uranium are used to heat liquid hydrogen inside a reactor, turning it into plasma, which is then expelled through a rocket nozzle to generate thrust.

Antimatter Engine

A visiual reprentation of Antimatter rocket

Have you ever heard about antimatter? In case you haven’t, antimatter is basically a material of antiparticle, with opposing charge of regular particles. An antimatter uses the product of the interaction between matter and antimatter as for propulsion. A report presented at the 39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit indicates that a two-stage antimatter engine powered rocket would need more than 800,000 metric tons of fuel to reach Proxima Centauri.

Although a single gram of antimatter would generate an immense amount of energy, producing that one gram would need 25 million billion kilowatt-hours of energy and a heck lot of dollars. Currently, human has only been able to create less than 20 nanograms of antimatter to date.

So, it’s clear that unless we make some extraordinary breakthrough in the area of propulsion, we might just be limited to our own solar system or we have to come up with a scary long term haul transit strategy.